In a cellular mobile communication network, frequency resources are required for a data transmission. However, the frequency resources are deficient and radio transmission environments are poor, thus how to allocate radio resources reasonably among multiple users and multiple services is a problem needing to be focused on in a system. Currently, there are several common resource allocation schemes as follows in the system.
Scheme 1) Fixed Resource Allocation
The concept of fixed resource allocation refers to allocating a certain number of radio resources to a user for exclusive use in a service until the end of the service. This scheme is commonly used in the 2nd Generation Telecommunication (2G) and primary 3rd Generation Telecommunication (3G) systems, where dedicated channels are mainly used, and mainly suitable for a circuit domain service. With regard to a packet domain service, since a packet is always arrived with burstiness and unpredictability, resource waste is easily to be caused with the fixed resource allocation scheme in a time period when no packet is arriving.
Scheme 2) Dynamic Scheduling
The basic concept of dynamic scheduling refers to determining which users are selected to be subjected to resource allocation at each scheduling time, according to information such as traffic volumes, priorities and channel conditions of various users. This scheme is commonly used in senior 3G and Long Term Evolution (LTE) systems and suitable for a burst packet service.
The essential process of dynamic scheduling is as follows.
A base station transmits resource scheduling signalling on a Physical Downlink Control Channel (PDCCH).
A UE detects the control channel and transmits data according to information in the resource scheduling signalling upon detecting that the resource scheduling signalling is for the UE.
FIG. 1 and FIG. 2 illustrate uplink and downlink dynamic scheduling processes by taking an LTE system for example.
As illustrated in FIG. 1, in the uplink scheduling process, firstly, the base station (e.g., eNode B (eNB)) transmits scheduling signalling on the PDCCH, wherein the scheduling signalling includes resource allocation information, transmission block format information and related Hybrid Automatic Repeat reQuest (HARQ) information and the like; secondly, the user equipment (UE) generates a corresponding uplink transmission block according to analysed scheduling signalling, and transmits the corresponding uplink transmission block to the eNB on the Uplink-Shared Channel (UL-SCH), wherein the timing relationship between the transmission on the PDCCH by the eNB and the transmission on the UL-SCH by the UE satisfies a scheduling timing sequence defined at a physical layer.
As illustrated in FIG. 2, in the downlink scheduling process, the eNB transmits PDCCH scheduling signalling and corresponding downlink service data in the same sub-frame, the UE obtains the resource allocation information, the transmission block format information, the associated HARQ information and the like by analysing the PDCCH, and receives and analyses corresponding transmission blocks on the Downlink-Shared Channel (DL-SCH).
The system allocates a Radio Network Temporary Identifier (RNTI) for each user, and the user determines whether it is being scheduled by determining whether the PDCCH carries the RNTI of the user. With respect to either uplink or downlink dynamic scheduling, because the system adopts the HARQ mechanism, a receiver after receiving and decoding a data packet will notify a transmitter of the decoded result through a feedback channel, so that the transmitter can retransmit a wrongly transmitted data packet in time, thus reducing a data transmission time delay.
Scheme 3) Semi-Persistent Scheduling
Semi-persistent scheduling is introduced based on the dynamic scheduling, and suitable for a service with a periodical data arrival and substantially constant data packet size, such as a Voice over IP (VoIP) service. The VoIP service includes an active state and a silent state, wherein voice packets arrive periodically at the active state and the period usually is 20 ms, and each voice packet is only several tens of bytes. If a dynamic scheduling mode is adopted for the VoIP service, the PDCCH needs to be independently transmitted for scheduling each voice packet, which will introduce great control overhead and reduce the number of users supported by the system.
In order to reduce the control overhead, and in consideration of the substantially constant voice packet size, a semi-persistent scheduling technology is introduced in the LTE system, and the principle thereof is as shown in FIG. 3, the resource allocation with semi-persistent scheduling is divided into two links, in one of which the cNB transmits Radio Resource Control (RRC) signalling for configuring a resource period and resources used for HARQ feedback, and in another one of which effective time of the semi-persistent resources and a frequency domain resource location are indicated by the PDCCH. The semi-persistent resource is periodically effective once being activated (in FIG. 3, the semi-persistent resource period is T), until it is released. With this scheme, excepting for activating semi-persistent resources, a PDCCH dynamic indication is not required for an initial transmission of a service packet (the indication is still needed in case of retransmission), thereby greatly reducing the control overhead.
As can be seen from the above, the dynamic scheduling is suitable for a packet service with strong burstiness and high data volume, so as to reduce the overhead proportion of control channels and increase the transmission efficiency; and the semi-persistent scheduling is suitable for a service with a regular data arrival and allocates periodical resources, so that a control channel indication is not required for an initial transmission of a data packet, thus reducing the control channel overhead.
Currently, the Internet of Things becomes the next hot trend of a communication system, the Internet of Things is organically combined with a cellular mobile communication network, and bearing for a part of services of the Internet of Things by virtue of a cellular radio network is an important technical branch.
Take a smart power grid for example, a large number of services therein such as electricity meter reading, electric power load monitoring, electric energy monitoring and the like can be born by a cellular radio network, and data analysis and control can be performed by background processing modules. These services are mainly characterized by low data volume, multi-terminal concurrency, and acquiring data as needed by a control system periodically or on demand.
Obviously, due to the low data volume, the control overhead with the dynamic scheduling will be much too high: and due to an unfixed period, allocating periodical resources with the semi-persistent scheduling will result in resource waste. Thus, the resource allocation schemes used currently will lead to excessive control overhead or resource waste in case of bearing a data interaction service with a low data volume and an unfixed period.